While most people seem to be using desktops less and smartphones more, I’m going in the opposite direction. I also dislike laptops and only use one if absolutely necessary for light travel. My Linux desktop computer has long since replaced separate gadgets like TV, radio, stereo system and gaming console. I would now like it to replace my phone too. (If I for some reason feel the need for a portable phone, I’ll just buy a separate “dumb” phone to carry in my pocket.) I also don’t see why I would need a separate external modem and router, if I have a large desktop case. 5G is coming, and while it probably won’t reach my isolated little island for some time, I would like to be able to insert a regular carrier’s SIM card directly into my desktop and maybe have the antennas on the roof on my cabin. How can I make this happen? What are internal modems/routers with SIM card slots called? (No protruding dongles, please.) Which ones are good? Where can I get them? What open source software do I need to configure and run them and maybe set up my own hotspot and VPN? Of course I would like the same box to function as an effective Safe node too. Any help would be appreciated.
No protruding dongles, suggests using one of the internal slots; that’s an odd choice as those are limited and there are many better gadgets for locating with the PC. So, depends on the motherboard but usually there will be PCIe slots and a “4g sim card pcie adapter” would cost more both for the card and the wasted PCIe.
I wonder the risk might be that the signal is not strong where the PC is located and if the SIM is internal there’s little option for extending to an aerial at a distance… it would be an antenna out the back protruding!
I would expect better that the SIM is best located with the router and ethernet or wireless then to the PC. I doubt you can easily find antenna to work on the roof paired with a SIM in the PC, in any way that is an advantage.
Also worth considering a decent router for strong fast wireless will be of a kind that might support two SIMs… so, option on subscribing to two networks, if you want to ensure connectivity… but that perhaps gets more complex if you need a stable IP address for a Safe node… and will obviously cost more for two services.
I can’t talk up 4G as my experience with Three is not good… flaky 4G tower here keeps dropping and a neighbour over the road with Vodaphone, has the exact same problem… they lock us into year+ long contracts and don’t bother to fix the hardware they share to provide the service… tea leaves!
… but if you’re on an island then it might be a good option for something.
Not sure I’ve added much value here… you’ve posted to /farming and for Safe node, mini PCs might work well … that’s if you don’t need sound and what graphics cards can do beyond cpus.
If you really want to get complicated and force the open source option, then look to “Openwrt Linux routers with sim card 4G”… but DIYing basic kit might be a lot more effort than reward; the router is not a problem, if your box is secure and your internal comms are through ssh etc.
and having rambled to this point, I see now you suggest “Of course I would like the same box to function as an effective Safe node too.” but that’s confusing me with the notion of SIM card in PC. So, you could have a mini pc with SIM as Safe node, more easily than a PC, as the mini pc could be located where there is a good signal and vncserver into that from a distance…
Perhaps what you’re seeking would follow from searching “linux openwrt router sim card 4g pcie”… but I’ve not seen Openwrt on internal cards, I guess necessarily it’s possible… if I was trying I would default to TP-Link brand external router for hacking but then I would refer to a forum like https://forum.openwrt.org/ likely then rethink 
I’m not looking for a mini PC. On the contrary I’m looking to build One large box that fits all the functionality I need in one unit - modem, router, gaming GPU, phone etc. I like having as few separate electronic gadgets as possible - preferably One - doing everything.
(Just like I like having as few guns as possible. Unfortunately there is no such thing as One gun for everything. But a 12/89 pump action shotgun, a .308 rifle, a .17 HMR rifle, and a .22 LR revolver together take care of pretty much everything that needs taking care of in Finland. And they all fit in one small closet. We don’t have elephants or buffalo.)
Elon Musk’s Starlink satellite internet service might work for you if your phone supports cell service over wifi. Starlink needs a certain number of satellites in service to cover the entire globe but some locations already have beta service and other areas are opening up pretty quickly as additional satellites are deployed.
But, but… that’s centralisation!
It’s like wrapping a router in tin foil…
The bit I can’t make sense of is the SIM being with the PC, risks that the 3/4/5G is weaker… there’s no extending a link to antenna as surely the length of that would lose signal.
You misunderstand me. Forget about my fairly remote location and connectivity. I spend time in our capital city too. I just want to build one large PC, the chassis of which can fit everything within, including a router and so on. I’m not sure it’s possible (just like with the guns), so that’s why I’m asking you guys for advice. Anyway, I have to go to bed now. There are fishing nets and traps to check tomorrow morning. Nighty night, people.
You can use a Mini PCI-E to PCI-E Adapter with SIM Card Slot and a 3G/4G or even 5G module.
If you need it, you can share this connection with other devices.
For example: How to share your 3g connection over Wifi on Ubuntu Linux
Now that’s what I’m talking about! Thank you, @digipl!
I’ll have to read up on this once I get done with my morning chores. I wonder if those cards could turn my desktop into a regular “old time” stationary phone as well with the right subscription and SIM card. That would be perfect, since my desktop stays on 24/7 anyway, and I don’t need the phone to be mobile. Would I need some additional software to make phone calls from my desktop?
In Finland we can get deals like these:
https://kauppa.telia.fi/yksityisille/tuotteet/liittyma.aspx?Subscription=Voice&Plan=Rajaton5G300M
Unlimited data, calls and text messages for 35 €/month.
Activating a modem for use with audio is challenging. Some have succeeded with very specific modems (mainly huawai) but it depends on the hardware.
A simple solution would be a second SIM of the same number on any device.
I like the idea of one box to unite them all but the physics says you would be better of with your SIM (or the antennae connected to that SIM) on your roof.
So one big box with a good aerial is the best compromise you will get.
I haven’t given the placement of the antenna much thought. Now I’m tethering through my Android phone. It is always connected to a wall socket and just sits there like an overly complicated modem filled with a bunch of “apps” and junk that I don’t need. If I decide to get rid of the “smart” phone it seems to me I might as well put the modem inside the computer case. But I sometimes do need to make phone calls too, even If I hardly ever answer the phone myself. It’s always muted. I can’t stand telemarketers.
I’m just trying to make things organized and have as few unnecessary running expenses as well as separate gadgets as possible. It seems to me a modem, whether internal or external, is just an access point that’s been crippled so I can’t easily use it for voice calls. And I don’t feel like paying Microsoft for making regular calls through Skype.
I dont pay for WhatsApp - insecure but used by many of my less IT-literate pals - or Signal – much more secure and used by Those Who Know.
I have a highish end modem/router kicking about that I think has a SIM slot on it - I’ll look it out and give you the model no.
Once I finish cooking - only at computer to check the recipie.
I would ditch the whole antiquated phone idea instantly if it weren’t for for the fact I occasionally have to talk to e.g. the police and the bank who definitely Do Not Know.
I found this post somewhat relevant to this topic, so I’m linking it here. Thanks @JPL!
I have read very little about it, but this looks like an interesting project. Do you, @Southside, have any insight into this?
https://freedomfi.com/
A quick glance suggests you will need more like $5k to set up a fully independent network - always assuming you have friends that also want to join in.
Having said that I think its an initiative that demands a closer look and possibly our support. It may be something that one day we could crowdfund, the numbers are not out of the realm of possibility.
@Sascha The bit-more-than-domestic router is a Zyxel VMG1312
It does not have a SIM slot but a USB connection that can take a SIM adaptor. Sorry for the uncertainty, its kit that was surplus from another project and I never got round to fitting it in here as I had higher end stuff also available - complete overkill for my present needs.
hopefully that will change 
If you want a router with USB modem support take a look at this page.
https://ofmodemsandmen.com/index.html
You have OpenWrt firmwares modified to work with USB modems for over a hundred routers.
I use this firmware on a cheap TP-Link router with a USB Huawei 4G modem, for a vacation home, and it works very well.
I’m using DD-WRT on the external Asus router I have in the city when I visit. But I’m fantasizing about something internal. And being able to make regular phone calls would be nice.